_Pac Brake Inopperatable

[hdeddie]

New update on my same problem,I decided to try and trouble shoot my inoperatable Pac Brake, on my 02' Sahara Safari,350 cummins ISC. Monaco tech said to change out the relays in the front run bay associated with the pac brake circuitry, about three of them, did that to no avali, then another tech from Masseys RV in Phoenix suggested that I pull the plate off of the Allison ICM on the left side consol and check the 2 10amp fuses, and swap the 3 relays on the top with the 3 on the botton, and see if that helped, it didn,t. So, off to the first RV shop, tech said he could fix it or find the problem, all he did was hot wire around everything and found thar the Pac can be accuated manually, I already knew that, 111.00 later, off to the local Freightliner dealer with a cummins tech and an Allison tech, 1 hr. in @ 110.00 per hr., tech says engin harness was modified from the factory,went from Catapillar to cummins in the change over, called cummins who sent illedgable schamatics to Freightliner, then they put their electrical guy on the problem, 4 hrs. later, he says that the ecm is seeing the signal but not communicating with the icm. So here we sit waiting for Monday when the tech said he would be contacting Allison(on his dime, since this was a learning experience on his part)and see if he could get some info from them,I had initially suggested that he simply rewire the whole pac brake circuit, but he's not sure that will work. Man I'm so frustrated, and getting deeper in debt with no end in sight. Anybody's input at this point would be greatly appreciated. Thanks for listning.

[RickO]

Sorry, I got nothing to say to help... but I do feel your pain.

Rick

[rdentist99]

Been there done that. Still not working. Went on 15 day road trip with wife and kids out west, over mountains and no one could get my PAC brake working either. Similar problem to yours. Some problem in the electrical signal. Didn't know about the two fuses in the console. Will look at those. Very frustrating. Will probably run new wire and make manual if i do anything. Tired of dumping money on the problem. No problem out west without PAC brake but wasn't pulling toad. 38' Monaco Windsor.

[1ciderdog]

I have I think a similar problem but not sure I really have a problem so will put it out for comments. When going down hill or coming to a stop with the pac brake switch in the on position and letting off the fuel the transmission shifts down to engine rpms above 2K (and continues to shift down as speed slows) but I can not tell that the pac brake actually engages. Should I hear a difference in engine sound? In trying to figure out if the butter fly in the pac brake activates I've manually downshifted to get the engine rpm above the 2K shift point, then let off the fuel and push the pac brake switch but do not hear or feel any difference. So the question is shouldn't I hear or feel the difference?
Thanks
Bob

[Skip426]

1cinderdog, yes , under the conditions you discribe you should feel and hear a difference. When my coach starts slowing with the engine/pac brake on if I allow it to keep slowing and downshifting , when it drops into second gear the rig nearly stands on its nose. To be sure you have a problem have someone rid in the rear over the engine and listen. Should hear a whistle from the exaust as the brake ingauges. Final proof tie a small piece of 10 lbs test fishing line on the rod that controls the butterfly and see if it snaps, have to be careful to put it where it can't melt.

[Jon from WI]

Ed, I am working on my pac-brake (96 Safari Serengeti) and have found some very valuable resources on the safari friends site (Yahoo Chat Group) If you can't find it, e mail me and I can hopefully get it for you.

[1ciderdog]

Skip426
Thanks for the suggestion of the 10 lbs. fishing line test - I'm sure that will be easier to interpret than what my wife would tell me if she goes back there to listen. While I do that I'll look for any loose vacuum line that could be a culprit. I've had exhaust brakes on both a Ford & a Dodge diesels and I could hear and feel the difference when activated.
Bob

[Skip426]

1Cinderdog, no vaccum line involved, system works on air pressure. While your under the coach trace the air supply line back, to the supply solinoid, mounted on the frame above the trans, and check your electrical hook up. Also fuses and relays in the circuit. I'm on access Freightliner , tracing circuits, and every time I crawl around my coach I find another fuse panel !
What ? You don't let your wife drive !

[1ciderdog]

Skip426 - We are traveling and in Colorado Springs for a few days so I'll check it out before we take off. We'll be heading west from here and it would be great to know the Pac Brake is functioning correctly before we hit those long downgrades.
Thanks Again
Bob

[David K]

If the pac brake has not been lubricated in a while (like at least once a year, if not more often) the butterfly can be frozen. Depending upon the amount of the seizure, it can be loosened up with proper lubrication (special high heat lubricant) and a small amount of force. If not, it might need replacing -- I am dealing with that right now on my rig as with the periodic lub job, the pac brake was not lubed.

[1ciderdog]

OK - I have found the problem (or at least a part of the problem.) The reinforced hose that runs to the Pac Brake had been to close to the exhaust system and had burned through allowing the pressure to escape. I've replaced that hose and hopefully resolved the problem. Dave, Last year I did buy lube for the Pac Brake from the vendor at a rally and I used it on the brake at least twice a year. I can move the butterfly valve but it takes a lot of leverage. Skip, Nope, wife doesn't drive it much and it always scares me when she does. Thanks guys for the help. I should know tomorrow or the next day if the problem has been resolved.
Safe travels
Bob

[1ciderdog]

If anyone is interested - the hose replacement resolved the problem. It is GREAT to have a working exhaust brake!
Safe Travels
Bob

[Skip426]

Safe travels, 1ciderdog.
hdeddie, sorry for hyjacking your thread, I hope you find a quick , inexpensive solution to your issues. Skip